Definition
Advisory Circulars (ACs) are non-regulatory documents issued by the FAA to provide guidance, recommended practices, and clarification on aviation topics. They explain how to comply with regulations, describe acceptable methods for meeting standards, and share information on subjects such as airworthiness, training, operations, and pilot techniques. ACs are not themselves regulations, but they are the FAA's official way of saying 'here is how we recommend you do this.'
Plain English
Advisory Circulars are FAA guidance documents that explain how to do things the right way. They are not rules you must follow, but they show you the FAA's recommended way of meeting the rules.
Context Anchor
Seen when instructors, pilots, and maintenance personnel look up FAA guidance on training, procedures, aircraft equipment, or compliance with aviation rules.
Derivation
Advisory' comes from the Latin advisare, meaning 'to give counsel.' 'Circular' refers to a document circulated to a wide audience. Together, the term simply means 'guidance shared broadly' — which is exactly what these documents are.
Why Pilots Care
ACs supply the detailed guidance instructors and pilots need to apply regulations correctly and maintain safety standards.
Intuition Check
Do not read advisory as meaning casual or unimportant. In FAA use, an advisory circular is official guidance, even though it is usually not a rule by itself.
Example Sentence 1
The instructor referred to the latest AC on stall and spin awareness when updating the lesson plan.
Example Sentence 2
ACs provide recommended procedures that help standardize training across different flight schools.